Diesel fuel, due to its performance, efficiency and safety advantages, is widely used in many types of transportation, such as trucks, trains, boats and aircrafts, as well as farm and construction equipment. On the other hand, diesel engines emit significant amount of soot (i.e., particulate matter), especially when running without enough oxygen, which draws a serious environmental concern.
Methods for decreasing soot emission from diesel engines have been developed by using additive components, such as methanol, alcohol, alkyl ethers (see, e.g., U.S. Pat. Nos. 2,089,580, 2,104,021, 3,270,497, and 5,425,790), bio-diesel and dimethyl carbonate (DMC).
Several attempts have been made to use DMC to treat diesel fuel. For example, U.S. Pat. No. 4,891,049 to Dillon et al. has described that diesel fuel containing 5% DMC has 10˜30% reduction of particulate emissions. U.S. Pat. No. 6,387,138 to Murayama et al. discloses that 10% DMC can suppress 50% or more particulate emission in diesel fuels. Other examples can be found in U.S. Pat. Nos. 2,311,386, 4,891,049, 4,904,279, and 5,004,480.
On the other hand, some features of DMC have precluded its wide use as a diesel fuel additive. For example, DMC separates from the fuel mixture at low temperatures, which may paralyze diesel engines. In addition, because DMC has a cetane number of 35˜36, which is lower than diesel fuel, excessive amount of DMC in diesel fuel will decrease the cetane number of the diesel fuel mixture, resulting in lowered performance and efficiency.
It is an object of the present invention to provide DMC-containing additive compositions to be used in diesel fuel that can suppress soot emission and at the same time solve the problems of phase separation and low efficiency.